Summary of Pavlov

Today a discernible tendency for the various schools of psychology to gravitate around two giant figures, Pavlov and Freud. Each represents one of the two possible definitive approaches to the study of the human mind---the objective, experimental method and the subjective introspective method. Pavlov stands for the first, Freud for the second. There are many intermediate approaches espoused by one or another school, but the current and growing trend is toward and ever sharper polarization.

Each of these magnetic poles lays exclusive claim to the title science of psychology. Each has powerful intellectual and institutional backing and exercises wide influence on a world scale. The question posed at the outset was “Which claim is backed by the evidence?” To find the answer, it was proposed to investigate the life and works of each. Here we summarize briefly the teachings of Pavlov, point out his significance.

The Teachings of Pavlov

The first twenty-five years of Pavlov’s long career as an experimental scientist were devoted to demonstrating that the nervous system controls the internal organic processes of blood circulation and digestion. As a result of this work, he made the first of a series of broad generalizations about the life processes of higher animals, including human beings. This first great generalization was that the brain, as the apex of the nervous system, regulates what he called the internal environment, the system of interrelated organs and glands, comprising the animal organism. As regulator of the internal environment, the task of the brain is to achieve and maintain a dynamic equilibrium within the body. This principle was called nervism. According to it, the body is a synthetic whole in which the parts are regulated and coordinated by the brain through the apparatus of the entire nervous system. To discover the facts and laws of the nervous control of the internal environment, a new experimental method was required, and Pavlov devised the method of the chronic experiment which allowed experimental work to be carried out on the intact and healthy animal.

The second broad generalization, made in the course of some thirty years of experimental work on dogs and primates, was that the nervous system, and particularly the brain, establishes and regulates the relationship between the animal organism and the external environment. Thus the brain is the special organs for the adaptation of animal behavior to the conditions of life. To carry out this task, there are two nervous mechanisms. The first is concerned with certain adaptive reflexes which, in the course of the evolution of the given species, have become hereditary. This is the mechanism of unconditioned reflexes. Unconditioned reflexes guarantee that the animal at birth will have minimal necessary behavioral adaptation to those more or less permanent conditions of life which have surrounded the species from its inception. The seat of the unconditioned reflex is the subcortex.

The second nervous mechanism to carry out the task of adapting behavior to the environment is the conditioned reflex. The discovery of this mechanism and its laws was perhaps Pavlov’s greatest achievement. By means of the conditioned reflex the animal is enabled to adapt to the constantly changing features of the environment during the course of its own life. It is a mechanism for “learning” from experience. Sense stimuli, through temporarily formed connections, act as signs representing concrete external objects. By means of this sensory system of signals, animals make the most refined adjustments to the details of the surrounding world. No matter how subtle this adaptive behavior of animals becomes, however, it can be fully accounted for in terms of sensory signals without calling on the human qualities of thinking, reasoning, feeling or purposeful activity. The oppositely acting processes of excitation and inhibition can make minute analyses of external agents by breaking down sense stimuli, and then can synthesize the latter into new conditioned reflex acts, resulting in new adaptations to the environment. The seat of all this conditioned reflex activity to the cerebral cortex.

In a third generalization, Pavlov combined the first two in grand synthesis: the nervous system, primarily the brain and in particular the cerebral cortex, has the function of establishing and maintaining a dynamic equilibrium between the external and the internal environments. On the one side, it controls and guides such vital activity as feeding, protection and reproduction, including the complex processes of hunting for food, avoiding enemies, finding a mate and the care and training of offspring. On the other side, the brain coordinates this external activity with various state of the body, and at the same time regulates all the internal functioning of the organism. Thus the nervous system---the brain, the cortex, with the mechanisms of the unconditioned and conditioned reflexes—controls and coordinates all the life processes, external and internal, of the animal.

From his work with mental patients in the clinic, during the closing years of his life. Pavlov made a fourth broad generalization: in human beings there is, in addition to the sensory system of signals which they have in common with animals, a system of signaling by means of speech. Words are conditioned stimuli standing as signs for the sensory signals. Thus the speech system is built up on the base of the sensory system, and cannot exist apart from it. It marks a qualitatively higher relation between the organism and the environment. For while animals can “learn” from their own experience by means of the sensory system of signals, people not only learn that way but in addition can learn from the entire experience of mankind through spoken or written words acting as speech signals, and passed on from generation to generation. As conditioned stimuli, words make abstraction and generalization from sensory signals possible. By combining words into grammatical sentences, and sentences into logical arguments, the speech system makes possible reflection of external reality in the human mind. Reflection, rested back in the sensory signals obtained in social practice, is found to be true or false, to correspond or not to correspond to reality. Thus the speech system makes possible the discovery of facts, laws and theories which truly reflect the nature of the external world. In short, the speech system, in closest relation to its base, the sensory system, is the nervous mechanism underlying thought, reasoning, purposeful activity and all forms of social consciousness, including technology, art and science. The human cerebral cortex is the seat of both the sensory and the speech systems of signaling reality.

Through his experimental work on animals and through his clinical work with mental patients, Pavlov was able to make a fifth broad generalization. The previous four generalizations concerned the regulative and adaptive functions of the nervous system, the brain and especially the cerebral cortex. The fifth, however, has to do with the protection of the nervous system and its apex. The cells of the brain, and in particular the cells of the cerebral cortex, are the most reactive of all the cells in the body, if not in all of nature, and therefore, are subject to periodic fatigue and to possible overstrain or to organic damage. There is of necessity a nervous mechanism for the protection of these vital cells. Pavlov called this mechanism protective inhibition. The most common form of protective inhibition is sleep. In sleep, inhibition spreads more or less rapidly through the cortex and down into the mid-brain to varying degrees. Its function is to restore from daily fatigue the reactivity of the cells of the nervous system, particularly of the brain and in cortex. A certain amount of protective inhibition in the form of sleep is required by the human organism during every twenty four hour period.

Another form of protective inhibition, far less common than sleep, may set in as a result of excessive strain, profound emotional shock or of sharp mental conflict. It is an inhibition of the reactivity of cells which have been subjected to overstrain due to extreme demands put upon them. The function of such inhibition, which may be more or less localized, is to protect the already overstrained cells from further stress which stress which might cause organic damage. This type of protective inhibition is one of the underlying higher nervous mechanisms of functional mental illness. Such illnesses involve no organic damage to the cortical cells, but the mechanism preventing such damage itself in many cases constitutes a pathological condition. Localized protective inhibition accounts for many kinds of neuroses and psychoses, from very mild to extremely severe cases.

A sixth great generalization concerned functional mental illnesses of all kinds. From his work in the laboratory on experimental neuroses and from his work in the clinic with psychiatric patients, Pavlov concluded that the syndromes of mental illness are manifestations of more or less profound disturbances of the higher nervous activity. He defined neuroses and psychoses as chronic disturbances of cortical and subcortical processes lasting weeks, months or years. Thus, while many non-Pavlovian psychiatrists tend to concentrate on the symptoms of the disease, the disturbed behavior, thought and speech of patients, Pavlov concentrates on the nervous disturbances underlying and giving rise to the symptoms. This analogous, on a very general level, to the difference between Marxist and non-Marxist political economists. Non-Marxists tend to concentrate on the appearances such as supply and demand, profit, wages and prices, while Marxists concentrate on the essential processes underlying and giving rise to the appearances, such as value, surplus value, value of labour power and value of the commodity. The symptoms of the various forms of mental illness are of great importance, and to the extent that non-Pavlovian psychiatry has discerned and clarified them, to that extent it has made a notable contribution to the science. But description and classification of appearances is only the initial stage of any science. A mature science is concerned with the essence of the given subject-matter expressed in verified facts and laws. Pavlov’s discovery of certain of the higher nervous mechanisms which produce the syndromes of functional mental illness laid the basis for the transformation of psychiatry from the stage of classification and abstract system building into a mature science.

Pavlov was a doctor of medicine and in all his scientific work there was one dominant motivating passion, to make a contribution to the theory and practice of medicine, and thereby to the relief of human suffering. Because it was concerned with the treatment of illness, his seventh and final broad generalization was, to him, the culminating point in his long career. From his work on the experimental neurosis in the laboratory, and from his work with mental patients in the clinic, he concluded that a number of those forms of functional mental illness, in which generalized or localized protective inhibition played a leading role could be improved, relieved or cured through heightening the protective inhibition by means of various drugs in proper dosage. In particular, he found that protective inhibition in the form of induced profound and prolonged sleep was a highly effective treatment of certain types of neuroses and psychoses. This treatment is called sleep therapy.

Such are broadest generalizations in the teachings of I. P. Pavlov. They form a rich heritage for the sciences of physiology, medicine, psychology and psychiatry. In addition, they contain important implications for pedagogy and philosophy, among other related areas of human knowledge.